Heavy machinery, motor vehicles and like major mechanical equipment, for the most part, are manually lubricated at a plurality of critical sites or points in accordance with published schedules of their manufacturer or industrial user. These schedules generally designate the frequency of such lubricative maintenance and the amount of lubricant to be applied as well as the noted sites of application. Where grease is the designated lubricant, a failure to perform scheduled maintenance not only places the operational capability of the machinery in jeopardy due to the frictional association of components, but also permits grease-type lubricants to commence to break down. In the latter regard typical grease-type lubricants comprise admixtures of oil and "soap," for instance an alkali metal such as lithium.
When permitted to remain without replenishment at a lubrication site over an extended interval of time, such lubricants degenerate to lose their lubricating ability and hinder mechanical performance. Due to the vagaries attendant with all scheduled manual maintenance schemes, due regard for the "human element" has prompted industry to look to automated lubrication. When incorporated, for instance, in tractor-trailer rigs, automated lubrication systems promise to extend the operational usefulness of mechanical components with an attendant realization of economy both from the standpoint of extended life spans and in a lowering of maintenance labor costs.
Of course, to remain effective, the automated lubrication system, itself, must be capable of operation under very high standards of reliability. For instance, the lubricant delivery system addressed to critical points of lubrication should be immune from overall breakdown due to an isolated breakage of, for example, only one of the delivery lines or the like. The reservoir from which the lubricant is dispensed should provide for sure delivery of lubricant to dispensing pumps and the like and remain isolated from harsh environments which may be encountered under highway conditions. Additionally, the dispensing pumps should incorporate a capability for dispensing predetermined amounts of lubricants to designated sites or locations. For instance, for a given type of equipment, certain groupings of these sites will require a greater quantity of lubricant than others. Further, the machinery and distribution system should exhibit high mechanical reliability over periods of extended performance.
Where electro-mechanical actuating techniques, for example, arrangements incorporating solenoid drives and the like, are utilized within the systems for purposes of actuating valves utilized, in turn, to control compressed air inputs to components, techniques are required for assuring the reliable performance of such valves themselves. The moving components of these valves should be periodically lubricated to assure their uninterrupted performance.
With the utilization of desirable electronic logic circuits for providing periodic actuation of the dispensing components of the systems, the noted reliability requirements carry over the such circuits themselves. While solid-state design techniques are available to provide extended circuit component lifespans, additional protective considerations arise. For example, where solenoid actuated valving is contemplated within a circuit design, the inductive loading nature of the devices normally will generate voltage surge phenomena which, without some form of protection, may deleteriously affect logic circuit components. Accordingly, considerations for long-term reliability of the electronic controls require appropriate accommodation for such phenomena.